U.S. patent application number 11/399876 was filed with the patent office on 2007-10-11 for system and method using multiple timing channels for electrode adjustement during set up of an implanted stimulator device.
Invention is credited to Kerry Bradley.
Application Number | 20070239228 11/399876 |
Document ID | / |
Family ID | 38576414 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070239228 |
Kind Code |
A1 |
Bradley; Kerry |
October 11, 2007 |
System and method using multiple timing channels for electrode
adjustement during set up of an implanted stimulator device
Abstract
Methods using multiple timing channels for electrode adjustment
during set up of an implanted stimulator device are disclosed. In
one embodiment, at least two conditions of electrodes (i.e.,
electrode combinations, pulse widths, pulse frequencies, pulse
amplitudes) can be "simultaneously" tested by providing each
condition in its own timing channel. In a preferred embodiment, the
pulses in each of the timing channels are interleaved and
non-overlapping to preserve the ability of the patient to assess
the therapeutic feel of both and to allow some time between pulses
for recovery. As well as allowing two sets of electrode conditions
to be gauged at the same time, the technique allows the electrode
to be manipulated during set up with ease and with a reduced
possibility of providing the patient with erroneous results. For
example, the two conditions in the two timing channels can comprise
initial and target final conditions, and transitioning between from
one to the other during device set up is facilitated as compared to
the prior art because concerns with electrodes having inconsistent
properties in both conditions are alleviated.
Inventors: |
Bradley; Kerry; (Glendale,
CA) |
Correspondence
Address: |
Wong, Cabello, Lutsch, Rutherfor & Brucculer L.L.P
20333 SH 249
Suite 600
Houston
TX
77070
US
|
Family ID: |
38576414 |
Appl. No.: |
11/399876 |
Filed: |
April 7, 2006 |
Current U.S.
Class: |
607/59 |
Current CPC
Class: |
A61N 1/36125 20130101;
A61N 1/36185 20130101; A61N 1/0551 20130101; A61N 1/0526
20130101 |
Class at
Publication: |
607/059 |
International
Class: |
A61N 1/00 20060101
A61N001/00 |
Claims
1. A method for adjusting electrodes on an implanted stimulator
device during set up, comprising: defining a first timing channel
which provides a first set of stimulation pulses to at least one
electrode on the implanted stimulator device; defining at least one
second timing channel which provides at least a second set of
stimulation pulses to at least one electrode on the implanted
stimulator device; and simultaneously activating the first and
second sets of stimulation pulses, wherein the first and second
sets of stimulation pulses are non-overlapping in the first and
second timing channels.
2. The method of claim 1, wherein simultaneously activating the
first and second sets of stimulation pulses comprises interleaving
the pulses in the first and second sets.
3. The method of claim 1, wherein the first and second sets of
pulses have the same frequency.
4. The method of claim 1, wherein the first and second sets of
pulses are non-overlapping so as to allow for recovery after either
of the pulses in the first or second sets.
5. The method of claim 1, wherein the first and second sets of
pulses are simultaneously activated using a wireless programmer
external to a patient in which the stimulator device is
implanted.
6. The method of claim 1, wherein the first and second timing
channels define which electrodes act as source or sink
electrodes.
7. The method of claim 1, wherein simultaneously activating the
first and second sets of stimulation pulses comprises first
activating the first set of stimulation pulses, and then adding the
second set of stimulation pulses to the already-active first set of
stimulation pulses.
8. A method for adjusting electrodes on an implanted stimulator
device during set up, comprising: applying a first set of
stimulation conditions in a first timing channel to at least one
electrode on the implanted stimulator device; and using a
programmer external to the implanted stimulator device to
wirelessly apply a second set of stimulation conditions in a second
timing channel to at least one electrode on the implanted
stimulator device.
9. The method of claim 8, wherein the first and second sets of
stimulation conditions define pulses of the same frequency.
10. The method of claim 8, wherein the first and second sets of
stimulation conditions define pulses of the same pulse width.
11. The method of claim 8, wherein the first and second sets of
stimulation conditions define pulses that are non-overlapping.
12. The method of claim 8, wherein the first and second sets of
stimulation conditions define pulses that are interleaved.
13. The method of claim 8, wherein the first and second timing
channels define which electrodes act as source or sink
electrodes.
14. A method for adjusting electrodes during set up of a stimulator
device implanted in a patient, comprising: defining a first timing
channel which provides a first set of stimulation pulses to at
least one electrode on the implanted stimulator device; defining at
least one second timing channel which provides at least a second
set of stimulation pulses to at least one electrode on the
implanted stimulator device; and using a programmer external to the
implanted stimulator device to gradually transition from activating
the first set of stimulation pulses to activating the second set of
stimulation pulses.
15. The method of claim 14, wherein the first and second sets of
pulses have the same frequency.
16. The method of claim 14, wherein the first and second sets of
pulses are interleaved.
17. The method of claim 14, wherein the first and second sets of
pulses are non-overlapping in the first and second timing
channels.
18. The method of claim 14, wherein the first and second timing
channels define which electrodes act as source or sink
electrodes.
19. The method of claim 14, wherein gradually transitiong from
activating the first set of stimulation pulses to activating the
second set of stimulation pulses comprises incrementally adding to
an amplitude of the second set of stimulation pulses.
20. The method of claim 14, wherein gradually transitiong from
activating the first set of stimulation pulses to activating the
second set of stimulation pulses comprises incrementally adding to
an amplitude of the second set of stimulation pulses while
incrementally subtracting from an amplitude of the first set of
stimulation pulses.
21. The method of claim 14, wherein gradually transitioning from
activating the first set of stimulation pulses to activating the
second set of stimulation pulses comprises incrementally adding to
an amplitude of the second set of stimulation pulses, and then
incrementally subtracting from an amplitude of the first set of
stimulation pulses.
22. A method for adjusting electrodes during set up of a stimulator
device implanted in a patient, comprising: defining a first timing
channel which provides a first set of stimulation pulses of a first
magnitude to at least one electrode on the implanted stimulator
device; defining at least one second timing channel which provides
at least a second set of stimulation pulses to at least one
electrode on the implanted stimulator device; and using a
programmer external to the implanted stimulator device to gradually
increase a magnitude of the second set of stimulation pulses while
maintaining the first magnitude of the first set of stimulation
pulses.
23. The method of claim 22, wherein the first and second sets of
pulses have the same frequency.
24. The method of claim 22, wherein the first and second sets of
pulses are interleaved.
25. The method of claim 22, wherein the first and second sets of
pulses are non-overlapping in the first and second timing
channels.
26. The method of claim 22, wherein the first and second timing
channels define which electrodes act as source or sink
electrodes.
27. The method of claim 22, wherein gradually increasing the
magnitude of the second set of stimulation pulses comprises
incrementally adding to the magnitude of the second set of
stimulation pulses.
28. The method of claim 27, further comprising, once the second set
of stimulation pulses increase to a second magnitude, using the
programmer to gradually decrease a magnitude of the first set of
stimulation pulses while maintaining the second magnitude of the
second set of stimulation pulses.
29. A method for adjusting electrodes on an implanted stimulator
device during set up, comprising: applying a first set of
stimulation conditions in a first timing channel to a first set of
electrodes on the implanted stimulator device; and gradually
applying a second set of stimulation conditions in a second timing
channel to a second set of electrodes on the implanted stimulator
device without modifying the first set of stimulation conditions in
the first timing channel.
30. The method of claim 29, wherein the first and second sets of
stimulation conditions define pulses of the same frequency.
31. The method of claim 29, wherein the first and second sets of
stimulation conditions define pulses of the same pulse width.
32. The method of claim 29, wherein the first and second timing
channels define which electrodes act as source or sink
electrodes.
33. The method of claim 29, wherein the first and second sets of
stimulation conditions define pulses that are interleaved.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to therapeutic electrical
stimulation systems and methods and, more specifically, relates to
adjusting electrodes during set up of an implanted stimulator
device.
BACKGROUND
[0002] Implantable stimulation devices are devices that generate
and deliver electrical stimuli to body nerves and tissues for the
therapy of various biological disorders, such as pacemakers to
treat cardiac arrhythmia, defibrillators to treat cardiac
fibrillation, cochlear stimulators to treat deafness, retinal
stimulators to treat blindness, muscle stimulators to produce
coordinated limb movement, spinal cord stimulators to treat chronic
pain, cortical and deep brain stimulators to treat motor and
psychological disorders, and other neural stimulators to treat
urinary incontinence, sleep apnea, shoulder sublaxation, etc. The
present invention may find applicability in all such applications,
although the description that follows will generally focus on the
use of the invention within a spinal cord stimulation system, such
as that disclosed in U.S. Pat. No. 6,516,227 ("the '227 patent"),
issued Feb. 4, 2003 in the name of inventors Paul Meadows et al.,
which is incorporated herein by reference in its entirety.
[0003] Spinal cord stimulation is a well-accepted clinical method
for reducing pain in certain populations of patients. As shown in
FIGS. 1 and 2, a Spinal Cord Stimulation (SCS) system typically
includes an Implantable Pulse Generator (IPG) or Radio-Frequency
(RF) transmitter and receiver 100 (collectively, "IPGs"), at least
one electrode lead 102 and/or 104 having a plurality of electrodes
106, and, optionally, at least one electrode lead extension 120.
The electrodes 106 are arranged in a desired pattern and spacing on
the lead(s) 102, 104 to create an electrode array 110. Wires 112,
114 within one or more leads(s) 102, 104 connect each electrode 106
in the array 110 with appropriate current source/sink circuitry in
the IPG 100.
[0004] In an SCS application, the electrodes lead(s) 102, 104 with
the electrodes 106 are typically implanted along the spinal cord 19
(FIG. 2B), and the IPG 100 generates electrical pulses that are
delivered through the electrodes 106 to the nerve fibers within the
spinal column. The IPG 100 body itself is normally implanted in a
subcutaneous pocket, for example, in the patient's buttocks or
abdomen. The electrode lead(s) 102, 104 exit the spinal column and
generally attach to one or more electrode lead extensions 120 (FIG.
2), which in turn are typically tunneled around the torso of the
patient to the subcutaneous pocket where the IPG 100 is implanted.
Alternatively, if the distance between the lead(s) 102, 104 and the
IPG 100 is short, the electrode lead(s) 102, 104 may directly
connect with the IPG 100 without lead extensions 120. For examples
of other SCS systems and other stimulation system, see U.S. Pat.
Nos. 3,646,940 and 3,822,708, which are hereby incorporated by
reference in their entireties. Of course, an IPG 100 is an active
device requiring energy for operation, which may be provided by an
implanted battery or an external power source.
[0005] Precise placement of the lead(s) 102, 104 relative to the
target nerves is important for achieving a satisfactory
physiological response, and for keeping stimulation thresholds low
to conserve battery power. A conventional lead implantation
procedure commonly places the leads 102, 104 parallel to the spinal
cord column 19 at or near the physiological midline 91, as is shown
in respective perspective and cross-sectional views in FIGS. 3A and
3B. More particularly, and as best shown in FIG. 3B, the electrode
leads 102, 104 are placed directly on the dura mater 51 within the
epidural space 70. (Cerebro-spinal fluid 72 is between the
electrode array 110 and the white matter 52 of the spinal cord 19.
Dorsal root nerves 50 are shown emanating from grey matter 53).
When the leads 102, 104 are placed on opposite sides of the
physiological midline 91 as shown, additional flexibility is
provided in the ability to recruit (i.e., stimulate) nerves in the
dorsal column, and to treat symptoms manifesting on either the left
or right sides of the patient's body.
[0006] In addition to precise placement of the electrode array,
proper selection of the electrodes, i.e., determining which of the
electrodes 106 in the array should be active in a given patient, is
critical for achieving effective stimulation therapy. However,
because of the uncertainties of the distances of the electrodes
from the neural target, the unknown nature of the specific
conductive environment in which the electrode is placed, etc., it
generally cannot be known in advance and with precision which
combination of active electrodes will be perceived by a patient as
providing optimal therapy. As a result, patient therapy generally
requires at the outset that various electrode combinations be tried
and feedback received from the patient as to which of the
combinations feels most effective from a qualitative standpoint,
what is referred to herein as IPG "set up."
[0007] Various electrode combinations and other stimulation
parameters can be tried during set up by programming the IPG 100,
for example using the clinician programmer 204 or a hand-held
programmer 202 (see FIG. 7, discussed below). For example, and as
best visualized in FIG. 3A, the IPG 100 can be programmed such that
electrode E1 comprises an anode (source of current), while E2
comprises a cathode (sink of current). Or, the IPG 100 can be
programmed such that electrode E1 comprises an anode, while E9
comprises a cathode. Alternatively, more than one electrode can be
used in both the sourcing and sinking of current. For example,
electrode E1 could comprise an anode, while both E2 and E9 can
comprise cathodes. Of course, the amount of current sourced or sunk
can also be programmed by the IPG 100. Thus, in the last example,
electrode E1 could sink 5 mA, while electrode E2 sources 4 mA and
electrode E9 sources 1 mA. The frequency of electrode stimulation
pulses, as well as the pulsewidth of such stimulation pulses, is
also programmable.
[0008] Ultimately, which electrodes are activated by the IPG 100,
and the polarities (cathode v. anode) and magnitudes (amount of
current) of those activated electrodes, are based largely on
patient feedback during IPG set up as noted earlier. Thus, the
patient, usually with the benefit of a clinician, will experiment
with the various electrode settings, and will report relative
levels of comfort and therapeutic effectiveness to arrive at
electrode settings that are best for a given patient's therapy.
[0009] Generally, and as one skilled in the art will appreciate,
cathodic stimulation across the dorsal column (e.g., across the
physiological midline 91) is preferable to cathodic stimulation
across the dorsal roots 50. What this means in FIG. 3A is that
cathodic stimulation from left to right (which promotes recruitment
of the dorsal column) is generally preferable to cathodic
stimulation from top to bottom (which promotes recruitment of the
dorsal roots 50). In other words, generally, it is preferable to
activate, for example, electrodes E1 and E9 (left to right, or from
lead 102 to lead 104) as cathodic sinks as compared to electrode E1
and E2 (top to bottom, or along either lead 102 or 104
individually). This being said, this is merely a preference and not
an inviolable rule, as ultimately which contacts are activated is a
matter of patient's subjective preference.
[0010] In the prior art, patients and/or clinicians used a
technique called "field steering" or "current steering" to try and
simplify the iterative process for determining a patient's optimal
electrode settings during set up of the IPG. See U.S. Pat. No.
6,909,917, which is incorporated herein by reference in its
entirety. In current steering, the current sourced or sunk by the
electrodes is gradually redistributed by the patient or clinician
to different electrodes using a single stimulation timing channel.
Such steering can be facilitated using some sort of user interface
associated with an external programmer 202 or 204, such as a
joystick or other directional device 206 (see FIG. 7). Examples of
current steering are shown in FIGS. 4 and 5. Starting first with
FIG. 4, assume that the IPG 100 has certain initial conditions,
namely that electrode E1 has been programmed to source 10 mA of
current, while electrode E9 has been programmed to sink 10 mA of
current. This initial condition might be arrived at after some
degree of experimentation, and might be a condition at which the
patient is feeling a relatively good response, but a response which
has not yet been fully optimized.
[0011] In an attempt at further optimization, current steering can
commence from these initial conditions. Thus, in FIG. 4, suppose
electrode E1 is selected and the current sourced from that
electrode is to be moved downward (e.g., by clicking downward on
the joystick). As shown, this moves 2 mA of sourcing current from
electrode E1 (8 mA) to electrode E2 (2 mA). Another downward click
moves another 2 mA, so that now E1 sources 6 mA and E2 sources 4
mA. Selection of sink electrode E9, followed by yet another
downward click moves 2 mA of sink current to electrode E10 as
shown. Current steering may also occur from left to right, i.e.,
from between leads 102 and 104. For example, it can be seen in the
last step of FIG. 5 that 2 mA of source current has been steered
from electrode E2 to electrode E10.
[0012] Gradual steering of the current in this manner (e.g., in
increments) is generally considered advisable to safeguard against
abrupt changes of the stimulation field which may be uncomfortable
or dangerous for the patient. For example, assume from the initial
condition in FIG. 4 that the patient feels relatively good
coverage. If this is the case, it might be useful to try moving the
cathode around, from E9 to either E2 or E10 for example, to see if
even better coverage could be afforded the patient. However, it
would generally be unadvisable to abruptly put the entirety of
electrode E9's sink current (-10 mA) onto electrodes E2 or E10.
Even though these electrodes are physically close to electrode E9,
to place the full sink current onto these electrodes could have
unforeseen and undesirable effects. Different nerves would
certainly be affected by such a change in electrode activation, and
it is not necessarily known how moving the full sink current would
affect those nerves. If the current when applied to the new
electrodes (e.g., E2 or E10) is too low (i.e., sub-threshold), no
clinical response would be noticed, even if the electrodes were
ultimately suitable choices. If the current is too high (i.e.,
supra-threshold), the result might be painful (or dangerous) for
the patient. Accordingly, incremental movement of the current was
considered the best approach.
[0013] However, such current steering, particularly in increments,
has drawbacks. For example, consider the hypothetical shown in FIG.
6. Suppose initially that the patient perceives good coverage from
the initial condition depicted in FIG. 6A, in which the active
electrodes are tightly clustered along one lead 102. As shown,
electrodes E1 and E3 each provide a 5 mA source current, while the
middle electrode, E2 sinks the sum of that current, 10 mA. These
initial conditions may suggest that a relatively similar
combination of electrodes, but shifted by one electrode (E2-E4),
would be reasonable to try as a target final condition, as shown in
FIG. 6B. Not only may such shifting of electrodes be advisable
during set up of the IPG 100, such adjustment may be necessary in
an once-previously-optimized system should the lead 102 or 104
longitudinally slip along the spinal column 19 due to patient
physical activity.
[0014] In any event, for whatever reason, it may be reasonable to
simply try applying the conditions on electrodes E1-E3 on
electrodes E2-E4. Using the current steering technique of the prior
art, and recognizing the advisability of incremental steering of
current between electrodes, the result of moving the conditions of
electrodes E1-E3 to electrodes E2-E4 is slow and subject to
erroneous results. Thus, as is illustrated in the sequential steps
of FIG. 6C, the settings for the electrodes had to be incrementally
"inch-wormed" into their new positions. Thus, the conditions at
electrode E3 are first moved to E4 over a series of incremental
steps. This is necessary to free electrode E3 to receive new
settings, because E3 can't simultaneously respond to its old and
new settings, i.e., electrode E3 cannot simultaneously source and
sink anodic and cathodic current, respectively. Then, once E3 is
free, E2's conditions are incrementally moved to E3. Then, once E2
is free, E1 is moved to E2 in like fashion. Thus, many steering
steps are required to fully move the initial conditions on
electrode E1-E3 to electrodes E2-E4. If nothing else, this is time
consuming and cumbersome.
[0015] More importantly, this method of steering the current during
set up in the hypothetical example of FIG. 6C can be subject to
erroneous results. Suppose that the initial conditions (FIG. 6A)
are a reasonable starting point for a particular patient, but that
the target final conditions (FIG. 6B) would be even better for the
patient. Because the prior art steering technique requires many
intermediary steps between the initial conditions and the desired
final conditions, it is possible that these intermediary steps
could inadvertently dissuade the patient from discovering the
benefits of the target final conditions. For example, notice that
in the intermediary steps, all four electrodes E1-E4 are utilized
to varying degrees. These intermediary steps do not necessarily
bear a good relation to either the initial conditions (generally
good) or the final conditions (even better). For example, in
intermediary step 111a, electrode E3 draws no current at all,
although in the final condition E3 should be drawing all of the
sink current (10 mA). It is therefore not surprising that
intermediary step 111a might not feel optimal for the patient.
Specifically, the patient may find the intermediary steps
uncomfortable, or the patient may not feel any stimulation effect
or therapeutic relief whatsoever. In short, there is a risk that if
the intermediary conditions are not perceived by the patient or
clinician during set up as steps taken in the "right direction"
towards more effective electrode settings, the plan to move the
settings to the final conditions may be abandoned, even though with
patience it would have been advisable to continue implementing this
plan.
[0016] Moreover, because in the particular example of FIG. 6C the
cathodic shifting occurs up and down along the lead, the negative
effect of non-optimal intermediary conditions is potentially
exacerbated. This is because movement of the cathode up and down a
particular lead will tend to recruit different dorsal roots 50. As
noted above, it is generally not preferred to stimulate the spinal
column in this manner.
[0017] Accordingly, what is needed is an improved method for
optimizing electrode activation during the set up of an implantable
stimulator device, and this disclosure provides embodiments of such
a solution.
SUMMARY
[0018] Methods using multiple timing channels for electrode
adjustment during set up of an implanted stimulator device are
disclosed. In one embodiment, at least two conditions of electrodes
(i.e., electrode combinations, pulse widths, pulse frequencies,
pulse amplitudes) can be "simultaneously" tested by providing each
condition in its own timing channel. In a preferred embodiment, the
pulses in each of the timing channels are interleaved and
non-overlapping to preserve the ability of the patient to assess
the clinical effect of both channels independently and to allow
some time between pulses for recovery. As well as allowing two sets
of electrode conditions to be gauged at the same time, the
technique allows the electrode to be manipulated during set up with
ease and with a reduced possibility of providing the patient with
erroneous results. For example, the two conditions in the two
timing channels can comprise initial and target final conditions,
and transitioning between from one to the other during device set
up is facilitated as compared to the prior art because concerns
with electrodes having inconsistent properties in both conditions
are alleviated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other aspects of the present invention will be
more apparent from the following more particular description
thereof, presented in conjunction with the following drawings, in
which:
[0020] FIGS. 1A and 1B show an electrode array and the manner in
which it is coupled to the implantable stimulator device in a
SCS.
[0021] FIGS. 2A and 2B show a placement of the percutaneous lead
for spinal cord stimulation with an in-line electrode array
inserted alongside the spinal cord in the epidural space, in close
proximity to the dura mater.
[0022] FIG. 3A and 3B show placement of two in-line electrode
arrays on the left and right sides of the physiological midline of
the spinal cord, respectively, in a perspective view and in
cross-section.
[0023] FIGS. 4 and 5 shows electrode current steering technique of
the prior art.
[0024] FIGS. 6A-6C show how current steering of FIGS. 4 and 5 could
be used in the prior art to move electrode settings to new
electrodes, albeit laboriously and with potential unsatisfactory
results.
[0025] FIG. 7 shows a block diagram illustrating exemplary
implantable, external, and surgical components of a spinal cord
stimulation (SCS) system in which the present invention can be
used.
[0026] FIG. 8 shows various components of the SCS system of FIG.
8.
[0027] FIG. 9 shows a block diagram illustrating the main
components of one embodiment of an implantable stimulator device in
which the invention can be used.
[0028] FIG. 10 shows a block diagram illustrating another
embodiment of an implantable stimulator device in which the
invention can be used.
[0029] FIG. 11 shows an example of various timing channels usable
in an implantable stimulator device, and shows whether each
electrode in a channel operates as a source or sink of current.
[0030] FIG. 12 shows a timing diagram according to an embodiment of
the invention in which two or more timing channels are used during
IPG set up to stimulate different electrodes in an interleaved
fashion.
[0031] FIGS. 13 and 14 show simple examples of how current may be
steered to new electrodes during set up using two timing
channels.
[0032] FIG. 15 shows how the example of FIG. 6C is more easily
handled in accordance with an embodiment of the invention in which
two timing channels are used during set up.
[0033] Corresponding reference characters indicate corresponding
components throughout the several views of the drawings.
DETAILED DESCRIPTION
[0034] The following description is of the best mode presently
contemplated for carrying out the invention. This description is
not to be taken in a limiting sense, but is made merely for the
purpose of describing the general principles of the invention. The
scope of the invention should be determined with reference to the
claims and their equivalents.
[0035] Before discussing schemes for the adjustment of active
electrodes during IPG set up that are the focus of this disclosure,
the circuitry, structure, and function of an implantable stimulator
device in which the technique can be used is set forth for
completeness.
[0036] The disclosed implantable stimulator device may comprise an
implantable pulse generator (IPG) or similar electrical stimulator
and/or electrical sensor that may be used as a component of
numerous different types of stimulation systems. More specifically,
the description that follows relates to use of the invention within
a spinal cord stimulation (SCS) system as an exemplary embodiment.
However, it is to be understood that the invention is not so
limited. Rather, the invention may be used with any type of
implantable electrical circuitry that could benefit from the
disclosed technique. For example, the present invention may be used
as part of a system employing a pacemaker, an implantable pump, a
defibrillator, a cochlear stimulator, a retinal stimulator, a
stimulator configured to produce coordinated limb movement, a
cortical or deep brain stimulator, or in any other stimulator
configured to treat urinary incontinence, sleep apnea, shoulder
sublaxation, etc. Moreover, the technique can be used in
non-medical and/or non-implantable systems as well.
[0037] Turning first to FIG. 7, a block diagram is shown that
illustrates the various components of an exemplary SCS system in
which the invention may be used. These components may be subdivided
into three broad categories: implantable components 10, external
components 20, and surgical components 30. As seen in FIG. 7, the
implantable components 10 include an implantable pulse generator
(IPG) 100, an electrode array 110, and (as needed) a lead extension
120 as described earlier. In an exemplary embodiment, the IPG 100,
described more fully below, may comprise a rechargeable,
multi-channel, telemetry-controlled, pulse generator housed in a
rounded high-resistivity titanium alloy case 116 (FIG. 1A) to
reduce eddy current heating during the inductive charging
process.
[0038] As seen best in FIG. 8, and as also illustrated in FIG. 7,
the electrode array 110 and its associated lead system typically
interface with the implantable pulse generator (IPG) 100 via the
lead extension system 120. The electrode array 110 may also be
connected to an external trial stimulator 140, through the use of a
percutaneous lead extension 132 and/or an external cable 134. The
external trial stimulator 140 typically includes the same or
similar pulse generation circuitry as does the IPG 100, and is used
on a trial basis, e.g., for 7-10 days, after the electrode array
has been implanted and prior to implantation of the IPG 100, to
test the effectiveness of the stimulation that is to be
provided.
[0039] Referring again to FIGS. 7 and 8, and as noted earlier, a
hand-held programmer (HHP) 202 may be used to control the IPG 100
via a suitable non-invasive communications link 201, e.g., an RF
link. Such control allows the IPG 100 to be turned on or off, and
generally allows stimulation parameters, e.g., pulse amplitude,
width, and rate, to be set by a patient or clinician within
prescribed limits during set up. The HHP 202 may also be linked
with the external trial stimulator 140 through another link 205',
e.g., an infra red link. Detailed programming of the IPG 100 is
preferably accomplished through the use of an external clinician's
programmer (CP) 204 (FIG. 7), which may also be hand-held and which
may be coupled to the IPG 100 directly via link 2011a or indirectly
through the HHP 202. An external charger 208, non-invasively
coupled with the IPG 100 through link 209, e.g., an inductive link,
allows energy stored or otherwise made available to the charger 208
to be coupled into the rechargeable battery housed within the IPG
100.
[0040] FIGS. 1A and 1B show the electrode array 110 and the manner
in which it is coupled to the IPG 100. As shown, the electrode
array 110 comprises first and second implantable leads 102 and 104
as described earlier. Leads 102 and 104 are in-line leads, meaning
that both consist of a plurality of in-line electrodes 106. The
electrodes are carried on a flexible body 108. In the illustrated
embodiment, there are eight electrodes on lead 102, labeled E1-E8,
and eight electrodes on lead 104, labeled E9-E16. The actual number
of leads and electrodes will, of course, vary according to the
intended application and should not be understood in any limiting
sense. As discussed above, leads 102 and 104 may be implanted into
a desired location, such as adjacent to the patient's spinal
column, through the use of an insertion needle or other
conventional techniques.
[0041] Each of the electrodes 106 on lead 102 are electrically
connected to the IPG 100 by a first signal wire 112 that extends
through, or is imbedded in, the associated flexible body 108.
Similarly, each of the electrodes 106 on the lead 104 are
electrically connected to the IPG 100 by second signal wires 114.
The signal wires 112 and 114 and/or the lead extension 120 are
connected to the IPG 100 by way of an interface 115. The interface
115 may be any suitable device that allows the leads 102 and 104
and/or lead extension 120 to be removably connected to the IPG 110.
Interface 115 may comprise, for example, an electromechanical
connector arrangement including lead connectors 117a and 117b (FIG.
1A) configured to mate with corresponding connectors (only
connector 119a is shown) on the leads 102 and 104. Alternatively,
the leads 102 and 104 can share a single connector that mates with
a corresponding connector on the IPG 100. Exemplary connector
arrangements are disclosed in U.S. Pat. Nos. 6,609,029 and
6,741,892, which are incorporated herein by reference. Although the
electrode array is shown as having two in-line leads 102, 104 each
with a plurality of electrodes 106 (e.g., 8 each), it should be
understood that more or fewer leads could be used. For example, a
single in-line lead with 16 linearly-arranged electrodes 106 could
be used as well.
[0042] Typically, the IPG 100 is placed in a surgically-made pocket
as described earlier, but of course may also be implanted in other
locations of the patient's body. Once implanted, the IPG 100 is
detachably connected to the lead system, comprising the lead
extension 120, if needed, and the electrode array 110. Once
implanted and any trial stimulation period is complete, the
electrode array 110 and lead extension 120 are intended to be
permanent. In contrast, the IPG 100 may be replaced when its power
source fails or for other reasons.
[0043] Turning next to FIG. 9, a block diagram is shown that
illustrates the main components of one embodiment of an implantable
pulse generator (IPG) 100 in which embodiments of the invention may
be used. As seen in FIG. 9, the IPG includes a microcontroller (IC)
160 connected to memory circuitry 162. The .mu.C 160 typically
comprises a microprocessor and associated logic circuitry which in
combination with control logic circuits 166, timer logic 168, and
an oscillator and clock circuit 164, generate the necessary control
and status signals to allow the .mu.C 160 to control the operation
of the IPG in accordance with a selected operating program and
stimulation parameters.
[0044] The operating program and stimulation parameters are
telemetered to the IPG 100, where they are received via antenna 250
(which may include a coil 170 and/or other antenna components),
processed, e.g., via RF-telemetry circuitry 172, and may be stored,
e.g., within the memory 162. The RF-telemetry circuitry 172
demodulates the signal it receives from the HHP 202 or CP 204 to
recover the operating program and/or the stimulation parameters.
More specifically, signals received by the antenna 250 are passed
through the transmit/receive switch 254 to amplifiers and filters
258. From there, the received signals are demodulated (262) using
Frequency Shift Keying (FSK) demodulation for example, and the data
is then sent to the microcontroller 160 for processing and/or
eventual storage. When RF-telemetry circuitry 172 is used to
transmit information to the HHP 202 or CP 204 to report in some
fashion on its status, the microcontroller 160 sends relevant data
to transmission drivers 256, where the carrier is modulated by the
data and amplified for transmission. The transmit/receive switch
254 would then be set to communicate with the transmission drivers
256, which in turn drive the data to the antenna 250 to be
broadcast.
[0045] The microcontroller 160 is further coupled to monitoring
circuits 174 via bus 173. The monitoring circuits 174 monitor the
status of various nodes or other points 175 throughout the IPG 100,
e.g., power supply voltages, current values, temperature, the
impedance of electrodes attached to the various electrodes E1 . . .
EN, and the like. Informational data sensed through the monitoring
circuit 174 may be sent to a remote location external to the IPG
(e.g., a non-implanted location) through telemetry circuitry 172
via coil 170.
[0046] The operating power for the IPG 100 may be derived from a
rechargeable power source 180, which may comprise a lithium-ion or
lithium-ion polymer battery, for example. The rechargeable battery
180 provides an unregulated voltage to power circuits 182. The
power circuits 182, in turn, generate the various voltages 184,
some of which are regulated and some of which are not, as needed by
the various circuits located within the IPG 100. In a preferred
embodiment, the battery 180 is charged by an electromagnetic field
created by an external portable charger 208 (FIG. 7). When placed
near the IPG 100 (e.g., centimeters away), an electromagnetic field
emanating from the portable charger 208 induces a current in
charging coil 270 (even through a patient's skin). This current is
then rectified and regulated to charge the battery 180. Further
associated with the charging circuitry is charging telemetry
circuitry 272, which is used for example by the IPG 100 to report
back to the portable charger 208 when the battery is full, and thus
when portable charger can be shut off.
[0047] In one exemplary embodiment, any of the N electrodes may be
assigned to up to k possible groups or "timing channels." In one
preferred embodiment, k may equal four. Moreover, any of the N
electrodes can operate, or be included in, any of the k timing
channels. The timing channel identifies which electrodes are
selected to synchronously source or sink current to create an
electric field in the tissue to be stimulated. Pulse amplitudes
(e.g., current, although an IPG may also put out a constant voltage
pulse) and pulse frequency of electrodes on a timing channel may
vary, e.g., as controlled by the HHP 202 and/or the CP 204.
[0048] For example, as shown in FIG. 11, four timing channels are
defined, and represent groups of electrodes that will be activated
as either sources or sinks at a particular time. Thus, in a first
timing-channel A, electrodes E1 and E4 will act as current sources
(denoted by the plus symbol), while electrodes E3 and E5 will act
as sinks (denoted by the minus symbol). Electrodes without any
designator in FIG. 11 are not activated and do not participate in
the sourcing or sinking of current. By designating different timing
channels in this manner, the stimulation provided to the patient
can be freely varied with desired therapeutic effect. See U.S. Pat.
No. 6,895,280, which is incorporated herein by reference in its
entirety. Note that the case 116 (FIG. 1A) of the IPG 100 can also
operate as an electrode which can source or sink current. This
allows the IPG to be operated in any number of different modes,
e.g., a monopolar mode (one electrode EX active with an active
case), a bipolar mode (two electrodes EX active), or a multipolar
mode (more than two electrodes EX active).
[0049] Ultimately, the grouping of the electrodes into different
timing channels is managed by the control logic 166 (FIG. 9), with
the timing of the activation of the various electrodes in each
channel being handled by the timer logic 168. The control logic
166, receiving commands from the microcontroller 160, further sets
the amplitude of the current pulse being sourced or sunk to or from
a given electrode. Such current pulse may be programmed to one of
several discrete current levels, e.g., between 0 to 10 mA in steps
of 0.1 mA. The pulse width of the current pulses is preferably
adjustable in convenient increments, e.g., from 0 to 1 milliseconds
(ms) in increments of 10 microseconds (.mu.s). Similarly, the pulse
rate is preferably adjustable within acceptable limits, e.g., from
0 to 1000 Hz. Other programmable features can include slow
start/end ramping, burst stimulation cycling (on for X time, off
for Y time), and open or closed loop sensing modes.
[0050] The stimulation pulses generated by the IPG 100 may be
charge balanced. This means that the amount of positive/negative
charge associated with a given stimulus pulse is offset with an
equal and opposite negative/positive charge. Charge balance may be
achieved through coupling capacitors CX, which provide a passive
capacitor discharge that achieves the desired charge-balanced
condition. Alternatively, active biphasic or multi-phasic pulses
with positive and negative phases that are balanced may be used to
achieve the needed charge balanced condition.
[0051] As shown in FIG. 9, much of circuitry included within the
IPG 100 may be realized on a single application specific integrated
circuit (ASIC) 190. This allows the overall size of the IPG 100 to
be quite small, and readily housed within a suitable
hermetically-sealed case 116 (FIG. 1A). The IPG 100 may include
feedthroughs to allow electrical contact to be individually made
from inside of the hermetically-sealed case with the N electrodes
that form part of the lead system outside of the case, as was
discussed above with reference to FIG. 1.
[0052] The telemetry features of the IPG 100 allow the status of
the IPG to be checked as noted earlier. For example, when the HHP
202 and/or the CP 204 initiate a programming session with the IPG
100 (FIG. 7), the capacity of the battery is telemetered so that
the external programmer can calculate the estimated time to
recharge. Any changes made to the current stimulus parameters are
confirmed through back-telemetry, thereby assuring that such
changes have been correctly received and implemented within the
implant system. Moreover, upon interrogation by the external
programmer, all programmable settings stored within the implant
system 10 may be uploaded to one or more external programmers.
[0053] Turning next to FIG. 10, a hybrid block diagram of an
alternative embodiment of an IPG 100' that may be used with the
invention is illustrated. The IPG 100' includes both analog and
digital dies, or integrated circuits (ICs), which may be housed in
a single hermetically-sealed rounded case having, for instance, a
diameter of about 45mm and a maximum thickness of about 10 mm. Many
of the circuits contained within the IPG 100' are identical or
similar to the circuits contained within the IPG 100, shown in FIG.
9. The IPG 100' includes a processor die, or chip, 160', an RF
telemetry circuit 172' (typically realized with discrete
components), a charger coil 270', a rechargeable battery 180',
battery charger and protection circuits 272', 182', memory circuits
162' (SEEPROM) and 163' (SRAM), a digital IC 191', an analog IC
190', and a capacitor array and header connector 192'.
[0054] The capacitor array and header connector 192' include
sixteen output decoupling capacitors, as well as respective
feed-through connectors for connecting one side of each decoupling
capacitor through the hermetically-sealed case to a connector to
which the electrode array 110, or lead extension 120, may be
detachably connected.
[0055] The processor 160' may be realized with an application
specific integrated circuit (ASIC), field programmable gate array
(FPGA), or the like that comprises a main device for full
bi-directional communication and programming. The processor 160'
may utilize an 8086 core (the 8086 is a commercially-available
microprocessor available from, e.g., Intel), or a low power
equivalent thereof, SRAM or other memory, two synchronous serial
interface circuits, a serial EEPROM interface, and a ROM boot
loader 735. The processor die 160' may further include an efficient
clock oscillator circuit 164', and (as noted earlier) mixer and
modulator/demodulator circuitry implementing the QFAST RF telemetry
method. An analog-to-digital converter (A/D) circuit 734 is also
resident on the processor 160' to allow monitoring of various
system level analog signals, impedances, regulator status and
battery voltage. The processor 160' further includes the necessary
communication links to other individual ASICs utilized within the
IPG 100'. The processor 160', like all similar processors, operates
in accordance with a program that is stored within its memory
circuits.
[0056] The analog IC (AIC) 190' may comprise an ASIC that functions
as the main integrated circuit that performs several tasks
necessary for the functionality of the IPG 100', including
providing power regulation, stimulus output, and impedance
measurement and monitoring. Electronic circuitry 194' performs the
impedance measurement and monitoring function.
[0057] The analog IC 190' may also include output current DAC
circuitry 186' configured to supply current to a load, such as
tissue, for example. The output current DAC circuitry 186' may be
configured to deliver up to 20 mA aggregate and up to 12.7 mA on a
single timing channel in 0.1 mA steps. However, it will be noted
that the output current DAC circuitry 186' may be configured to
deliver any amount of aggregate current and any amount of current
on a single timing channel, according to one exemplary
embodiment.
[0058] Regulators for the IPG 100' supply the processor and the
digital sequencer with a voltage. Digital interface circuits
residing on the analog IC 190' are similarly supplied with a
voltage. A programmable regulator supplies the operating voltage
for the output current DAC circuitry 186'. The coupling capacitors
CX and electrodes EX, as well as the remaining circuitry on the
analog IC 186', may all be housed within the hermetically sealed
case of the IPG 100. A feedthrough pin, which is included as part
of the header connector 192', allows electrical connection to be
made between each of the coupling capacitors CN and the respective
electrodes E1, E2, E3, . . . , or E16.
[0059] The digital IC (DigIC) 191' functions as the primary
interface between the processor 160' and the output current DAC
circuitry 186', and its main function is to provide stimulus
information to the output current DAC circuitry 186'. The DigIC
191' thus controls and changes the stimulus levels and sequences
when prompted by the processor 160'. In an exemplary embodiment,
the DigIC 191' comprises a digital application specific integrated
circuit (digital ASIC).
[0060] With the basic structure of an implantable stimulator
understood, focus now shifts to a detailed description of the
multi-channel electrode adjustment techniques that are the focus of
this disclosure.
[0061] Embodiments of the present invention take advantage of a
feature present in some implantable stimulator devices, namely
multiple timing channels. While multiple timing channels have been
recognized as useful in the context of providing improved
stimulation during actual useful therapeutic operation of the
implantable stimulator, (see [CITE], which are incorporated herein
by reference in their entireties), it is not believed that multiple
timing channels have been used during set up of the IPG, i.e.,
prior to actual useful therapeutic operation.
[0062] One basic implementation of using multiple timing channels
during set up is illustrated in a simple example with reference to
FIG. 12. In this example, two different timing channels are used
during IPG set up, A and B. As can be seen, timing channel A
activates electrode E1 as the cathode (current sink) and the case
of the IPG 100 as the anode (current source). Timing channel B
activates electrode E2 as the cathode and the case as the anode. Of
course, the timing channels A and B will, in addition to active
electrodes, also specify other stimulation parameters pertinent to
the channel, such as pulse width (W), pulse amplitude (A), and
pulse frequency (f). The timing channels may also specify the
nature of charge recovery 199' (active or passive) to occur after
each stimulation pulse 199. Charge recovery is well known in the
art of implantable stimulators and requires no further elaboration,
other than to note in FIG. 12 that passive charge recovery 199' is
shown for illustrative purposes only.
[0063] Timing channels A and B in the simple example of FIG. 12 are
respectively akin to the initial condition and final conditions
discussed in the Background section of this disclosure. Because
different timing channels are used, with no one electrode being
simultaneously activated in the timing channels, the initial
condition of timing channel A and the final condition of timing
channel B can essentially be simultaneously tested (at least from
the patient's point of view). Moreover, as will be made apparent
later, such "simultaneous" testing of the conditions during set up
can be accomplished much more quickly and efficiently than was
possible in the prior art as illustrated in FIGS. 4-6. As also will
be seen, the ability to "simultaneously" testing two different
electrode conditions within two different timing channels allows
for the electrodes to be tested and manipulated during set up with
relative ease and without the potential for erroneous results.
[0064] In the embodiment of FIG. 12, such "simultaneous" testing of
initial and final conditions is made possible by interleaving the
pulses active in each timing channel. Thus, the pulses in timing
channel B are activated at a time Ta-b after the pulses in timing
channel A are activated. In this example, this means that the
frequency, f, of the pulses in timing channel B is equal to the
frequency of the pulses in timing channel A. Moreover, other
stimulation parameters (pulse width, pulse amplitude) are the same
as between the two channels, although this is not strictly
required, especially as concerns pulse amplitude which will be
discussed in further detail below. In short, and as will eventually
be made clear, the stimulation parameters specified for the two (or
more) timing channels can be wholly different, so long as no
particular electrode is called upon to be simultaneously active in
two different timing channels.
[0065] In a preferred embodiment, it is preferred that the time
between pulses in the various timing channels, i.e., Ta-b or Th-a,
be greater than or equal to 3 milliseconds. This is desired to
allow for current recovery, be it passive (199') or through an
active attempt to source/sink the same charge sunk/sourced from a
particular electrode (not shown), as well as to allow the nerves
time to recover between pulses.
[0066] FIG. 13 illustrates an embodiment of the disclosed use of
multiple timing channels as applied to the Example of FIG. 12. In
FIG. 13, the goal during set up is to move the initial conditions
from FIG. 12 (E1/case) to the desired final conditions (E2/case) to
see if such steering improves patient therapy. Accordingly, as
before, the electrode to be steered (i.e., E1) is selected. When
the patient or clinician uses an external programmer 202 or 204,
such as a joystick or other directional device 206 (see FIG. 7), to
move some portion of the current from electrode E1 to electrode E2,
the current is so moved as FIG. 13 illustrates. However, this moved
current appears in a different timing channel: whereas electrode
E1's current was sourced in timing channel A, the moved current to
electrode E2 is sourced in timing channel B. Subsequent downward
clicks will move more of the of the current from E1 in timing
channel A to E2 in timing channel B until, five clicks later in the
example, the final conditions are reached in which all 10 mA of the
source current is a transferred from electrode E1 to electrode
E2.
[0067] It should be noted that the same "incremental" current
movement approach is illustrated in FIG. 13 as was illustrated in
the prior art. In other words, not all 10 mA of the E1's current
was moved to E2 in timing channel B in one "click." For the reasons
described earlier, such abrupt steering of all of the current in
this manner could be at least uncomfortable for the patient.
However, while an incremental approach is preferred for this
reason, it is not strictly necessary, and the entirety of the
current in timing channel A can be moved or duplicated in the
second timing channel B in other useful embodiments. Moreover, as
shown in the example of FIG. 13, the current transferred to
electrode E2 in timing channel B is subtracted away from the
current of electrode E1 in timing channel A, specifically, in 2 mA
increments. However, this is not strictly necessary, and instead
the full current (10 mA) can remain in timing channel A even as the
current is gradually built up in electrode E2/timing channel B, as
shown in the left half of FIG. 14. Thereafter, once the full
current has been gradually established in electrode E2/timing
channel B, the current in electrode E1/timing channel A can be
gradually reduced, as shown in the right half of FIG. 14.
[0068] At this point, it can be appreciated even through the simple
example of FIGS. 13 and 14 that the disclosed multi-channel set up
technique has significant advantages when compared to the prior
art. Significantly, the use of two timing channels allows two
potentially-viable sets of stimulation parameters to be applied to
the patient during set up in an interleaved fashion. So applied,
the patient will independently feel the effects of both of the
setting of both timing channels, but in a manner that does not blur
the effect of two. By contrast, in the prior art, the gradual
steering of current from E1 to E2 (continuing the current example)
would inevitably involve intermediate states in which both E1 and
E2 were simultaneously sourcing current in a signal timing channel.
Such intermediary states, as noted earlier (see FIG. 6C, 11 la),
have the potential to recruit different nerves that would not be
recruited in the initial (presumably good) and final (possibly even
better) conditions. In other words, such intermediary conditions
may inadvertently gravitate away from potentially useful therapy,
and it is thus beneficial that embodiments of the disclosed
technique do not involve such intermediary states.
[0069] FIG. 15 illustrates an embodiment of the disclosed technique
in the context of the example introduced earlier in FIG. 6. By way
of review, the example of FIG. 6 involved shifting a tightly-group
initial condition along a single lead 102 in which electrodes E1
and E3 each provide a 5 mA source current, while the middle
electrode, E2, sinks the sum of that current, 10 mA (see FIG. 6A).
As discussed earlier, during IPG set up, an assuming the initial
conditions suggest generally satisfactory therapy to the patient,
it might be desirable to shift this initial condition down the lead
102 to a final condition involving electrodes E2 to E4 (see FIG.
6B). Again by way of review, it was discussed that such shifting of
the electrodes previously required many intermediary steps, so that
the conditions of the various electrodes could be incrementally
inch-wormed into position (see FIG. 6C). This approach was time
consuming, and required passing though many intermediary steps not
truly indicative of either the initial or desired final conditions
(e.g., 111a, FIG. 6C), and therefore which might be perceived
poorly by the patient.
[0070] As shown in FIG. 15, this example is much more easily and
reliably handled using an embodiment of the disclosed multi-channel
set up technique. As shown, the initial conditions (E1-E3; 550) are
assumed. Once a plan has been formulated to switch the conditions
to E2-E4, the patient or clinician can select the electrodes of
interest, i.e., E1-E3 in this example, using an appropriate user
interface as described earlier. Then, using (for example) the
joystick or other directional device 206 (see FIG. 7), the user can
click downward to move some of the current into electrodes
associated with timing channel B. In this regard, it is assumed
that timing channels A and B have already been somewhat pre-defined
in their stimulation parameters, and that movement of the joystick
operates to shift current to the new timing channel. For example,
as a default, it may be the case that timing channel B has the same
frequency and pulse width as in timing channel A. Moreover, the
external programmer 202 or 204 may automatically set the delay
between the pulses in the two timing channels (Ta-b and Tb-a) to be
equal, such that the pulses in timing channel B are positioned
exactly in the middle of the pulses of timing channel A. Of course,
Ta-b and Th-a need not be equal, and this suggestion is therefore
merely exemplary. The important thing in setting the timing of the
pulses is to ensure that the pulses in the two timing channels do
not interfere with each other. Hence, some minimal amount of time
is advisable (e.g., 3 ms) to allow for current and nerve tissue
recovery, for example. Ultimately, programming the parameters of
the various timing channels during set up and the operation of the
joystick can be accomplished with the assistance of one of the
external programmers such as HHP 202 or CP 204 (see FIG. 7).
[0071] Once the system is enabled to handle at least two timing
channels during set up, and once the electrodes to be manipulated
are selected, adjustment of the electrodes can occur as shown in
FIG. 15. As shown, clicking down on the joystick represents
movement of some amount of current to new electrodes in timing
channel B. Thus, as shown, upon the first click, an incremental
amount of current is preferably placed on the final condition
electrodes (E2-E4) (551) in timing channel B. (In this example, and
as is different compared to earlier examples, the increment of
current used is 2.5 mA for ease of illustration, although of course
no particular increment of current is important to any embodiment
of the invention). As depicted in FIG. 15, establishment of current
in timing channel B does not immediately affect the amount of
current in the initial conditions of timing channel A, similarly to
the left side of FIG. 14. (This is different from the example of
FIG. 13, in which current was subtracted from timing channel A and
added to timing channel B, amounting in a constant amount of
current when the two channels were summed). Subsequent clicks
increase the incremental current, until the amount of the current
on the final condition electrodes in timing channel B (E2-E4)
matches that of the initial condition electrodes in timing channel
A (E1-E3) (552). Further subsequent clicks then incrementally
remove the current from the initial condition electrodes in timing
channel A, which eventually leaves as active only the final
condition electrodes in timing channel B (553).
[0072] At this point, timing channel B, the only currently active
timing channel, can be viewed as or reset to the primary timing
channel, such that further use of the method will work to move some
amount of current back to electrodes in timing channel A, or to
electrodes in another new timing channel C, etc. Moreover, use of
the disclosed technique can also be used with the prior art
technique. In other words, the patient or clinician using HHP 202
or CP 204 can program the IPG during set up such that steering the
current will involved physical movement along the electrode array
110 in one timing channel, or will move current to a new timing
channel. Because it may still be useful to move current in both of
these types of ways, embodiments of the invention may indeed use
both ways.
[0073] As can be seen from FIG. 15, movement from the initial
conditions to the final conditions is greatly facilitated when
compared to the technique of the prior art (FIG. 6C). Moreover, and
as noted previously, the disclosed technique does not suffer from
the same problem of intermediary steps during which the electrodes
are really not indicative of either the initial or final conditions
(FIG. 6C, 111a), and which may discourage the patient or clinician
during set up away from useful optimization for the electrodes.
[0074] It should be noted that in useful embodiments of the
disclosed multi-channel set up technique, the pulse amplitudes
(i.e., current) in the various timing channels can be affected
differently from what is illustrated in the various examples. For
example, the amount that current is incremented or decremented in
the various active electrodes in the various timing channels can
vary and need not be a set value. For example, larger increments
can be used in initial steps, with smaller increments used as
various target conditions are approached.
[0075] Also, amplitude adjustment may be made independently of the
use of the disclosed technique. For example, it cannot be assumed
in FIG. 15 that the total source current of the initial condition
electrodes (10 mA) would be optimal when applied to the final
condition electrodes. After all, differing electrodes will recruit
different nerves with different thresholds, and therefore may
require different pulse amplitudes to achieve the same basis
therapeutic effect (e.g., paresthesia). Accordingly, other
traditional pulse amplitude (i.e., current) adjustment mechanisms
(not shown) can also be used in conjunction with the disclosed
technique. For example, after performing the steps as shown in FIG.
15 (e.g., after 553), or even at some intermediary step, it may be
advisable to globally adjust the currents. For example, after
completing the steps as shown in FIG. 15, it may be advisable to
adjust the total source current from its initial value of 10 mA to
higher (e.g., 12 mA) or lower (e.g., 8 mA) values. Such traditional
means of adjusting the current would employ programming of the HHP
202 or CP 204 (FIG. 7) as is well known.
[0076] The disclosed technique can involve other stimulation
parameters changes as well. For example, during performance of the
steps in FIG. 15, the frequency of the pulses can be made to
change. For example, if the initial condition frequency of the
pulses (550) is f, intermediary steps (551) could take place at
0.75f, while the middle step (552) occurs at 0.5f. Such adjustment
(lowering) of the frequency would be sensible at step 552, as the
conditions at that point (absent adjustment) are essentially
equivalent to a stimulation frequency of 2f (albeit with different
electrodes). As the steps continue (e.g., to 553), the frequency
can gradually be brought back down to f.
[0077] It should be understood that reference to an "electrode on
the implanted stimulator device" includes electrodes on the
implantable stimulator device, or the electrodes on the associated
electrode leads, or any other structure for directly or indirectly
stimulating tissue.
[0078] While the invention herein disclosed has been described by
means of specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled
in the art without departing from the literal and equivalent scope
of the invention set forth in the claims.
* * * * *